Screen printing machine



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his a? orn ey I Fatented June 26, 145

SCREEN PRINTING Lian William A. Maher, Glencoe, Ill.

Application July 12, 1944, Serial No. 544,530

((31. Nib-122) 12 Claims.

This invention relates generally to screen printing machines and in particular to such machines using silk screens. The process of silk screens printing is old, one of the favored methods being to impregnate the screen with a gelatin compound, chemically fix a design thereon, wash out the unaffected portions, leaving a stencil, through which paint or ink is forced usually by a squeegee, thereby transferring the design to a designated object.

To perform this operation by hand, with a squeegee and screening frame is slow and tedious. In applying mechanical means, aproblem is immediately presented of substantially reducing or eliminating the destruction of the silk screen by friction with parts of the machine.

A specific purpose of my invention is to provide a support for the screen by means of a continuous belt made of rubber or other suitable material, moving over a. series of rollers in direct contact with and supporting the silk screen and both moving at the same speed, so as to eliminate friction between the screen and belt.

A further purpose of my invention is to provide a support for the screen by means of a continuous belt but separated from the screen at a narrow zone to permit the feeding of the printing material to the inside of the screen where it is distributed and forced through the screen by a squeegee.

A further purpose of my invention is to facilitate the use of rapidly drying printing materials like lacquers, where such materials are desirable in the printing process. In the use of quick drying printing materials with a large surface of the screen exposed to the air, the printing material drys in the stencil openings, clogging the screen. In the use of a screen, the printing materials are introduced or placed upon the screen on its upper or inner surface, the bottom or outer surface being placed in contact with the work piece receiving the design. In my invention, by supporting the screen on its inwardly facing surface by a belt substantially throughout its entire area, with the assistance of the viscous nature of the printing material, the air is excluded, and which prevents the drying of the printing material upon the screen during operations.

With the above objects in view, my invention is illustrated by the drawings, though it is to be understood that changes may be made in the exact form disclosed without departing from the spirit and scope of the invention.

in the drawings, similar numerals refer to similar parts through the several views.

Figure 1 presents a top view of the machine.

Figure 2 presents a side view of the machine.

Figure 3 is a vertical cross-section view taken on the plane of the line 2--2 of Figure 2, showing in particular the form and assembly of the various parts comprising the printing cylinder.

Figure 4 is a vertical cross-section view of the printing cylinder taken on the plane of the line 3-3 of Figure 3.

Figure 5 is a diagrammatic view on reduced scale showing the screen rotated about 45 beyond its position in Figure 4.

Figures 1 and 2 are included to show a suggested complete machine embodying my invention and consisting of a rectangular steel frame I supported upon legs l6, with braces ll, so arranged as not to interfere with the passage of the H frame Hi. The printing cylinder is supported upon this frame I by an H frame l0 moved backwards and forward by means of a worm screw 6 attached to the frame I and supported by the brackets 5 and H and the screw threads 21, the screw 6 being operated by a motor and reversing mechanism not shown. An axle I4 is supported in the hubs 88 in the end frames of the H frame I0 and fixed in its position by the key St. A gear 20 of the approximate diameter of the printing cylinder, turning freely on the axle M and provided with a lug II to engage the clutch lug 8, is in constant mesh with the rack 1, attached to the frame I.

The screen cylinder consists of the circular end plate 26 fastened in any suitable manner, as by welding, for example, to the sleeve 34 which also supports the clutch lug 8 held in position by the pin 22 and against the gear lug 2! by the spring 28. The annular ring 30 and the circular plate 26 are connected by the curved plate 29 and over which the silk screen 9, secured at its margins to a flexible metal frame not shown, is stretched and fastened to the plate 29 by the clamping strips II and stud bolts 43, forming a single headed drum, supported by and turning freely upon the axle M. The side margins of the screen are secured in a flexible frame, not shown, and this frame is secured in any suitable manner to the end plate 26 and annular band 86 to keep the screen taut.

The structure for supporting the rubber belt, designed to operate within the screen cylinder, consists of the circular end plate 48 integral with a sleeve 35 fastened to the circular end plate 32 by means of bolts 36, said end plates having several openings permitting access to the inside of said drum and having one in particular, at It tion upon for the purpose of inserting the paint, ink or other printing material. The two end plates 48 and 32 are held against rotation by a set screw 31 in the sleeve 35 or by other suitable means, contacting the axle H.

A plurality of rollers I! supported by the end plates 48 and 32 in holes 42 therein, support an endless belt 28 of rubber or other suitable material in substantially constant contact with the screen 8, except at the narrow zone where the printing material is applied, said belt passing over the driven roller 88 and idle roller 45, the idle roller 48 having an adjusting means I! for removal of the slack. The idler roller 41, having a means for adjustment, presses against the belt as it passes over the driven roller 38 preventing slipping and also assisting in the transfer of any printing material on the belt to the roller 83 for removal by the doctor blade 44. A squeegee I8 is supported in a stationary posithe stationary end plates 48 and 82 so as to contact the screen at a point on a line substantially normal to the plane of the work table 4, as the screen rotates distributing the paint or other printing material 40, through the screen upon the object receiving the design. A doctor blade 44, in contact with the roller 88, removes any excess accumulation of printing material.

The roller "i3 is driven by a gear 39 fastened co-axially to one end thereof in mesh with the ring gear 25, the latter being fastened to the end plate 28 by the machine screws 24, said gears having a pitch ratio which assures the belt 28 travelling at substantially the same speed as the screen 8. in order to avoid friction or wear,

upon the screen.

A work table 4 is automatically raised and lowered by hydraulic or cam means located at l8 but which need not be here described. By such mechanism, the work to receive the design may be raised to a proper level to contact the silk screen and may be lowered to permit the passage of the member 2!.

In operation, the carriage I8 is moved forward by the screw 8 or to the right as Figure 1 is viewed, the gear 88 being in mesh with the stationary rack 1, rotates and through the clutch 8, revolves the screencylinder and screen 8, which is supported by the belt 88, passing over the rollers l2 and driven at the same speed as the screen by the roller 88 and gears 24 and 38.

illustrated are by way of The squeegee forces the paint through the screen,

thus depositing the design upon the workpiece 48, as shown in diagrammatic Figure 5, placed upon the work table 4, which work table is automatically raised and lowered at the commencement and end of the operation so as to be in contact with the screen, and also permit a complete revolution of 880 and clearance of member 28 in the return operation, the carriage being returned by the reverse motion of the screw, and

Y the ratchet clutch 8 assuring a stationary position of the printing cylinder during this part of the operation. The machine is then in position to repeat the operation.

While I have mentioned rubber for use infthe supporting belt, any material, substantially nonelastic, woven, moldedor otherwise, may be used to support the printing screen. The screen itself is preferably made of silk, but may be any other material suitable for the purposes.

The belt supports the screen throughout the entire area of the screen, except within the limited area of the printing zone, where the belt is separated from the screen, which then passes under the squeegee. As the printing cylinder rolls across the top surface of the one or more work pieces which are supported at the proper level on the work table, any tendency of the screen to stretch or warp cannot extend beyond the printing zone at the margins of which the screen and supporting belt are in intimate 'con tact with each other.

Due to this contact and the presence of some paint or printing material'on either or both the screen and the belt, no slippage of the screen relatively to the belt, or warping of the screen, can occur, thus improving the accuracy of the work and prolonging the life of the screen.

While the foregoing description discloses what I believe to be a preferred and practical embodin'ient of my invention, it will be apparent and understood to those Skilled in the art, that the specific details of construction as described and illustration, and not to be construed as limiting the scope of the invention and that modifications and alterations may be practiced within the scope of the appended claims.

What I claim as my invention is:

1. In a screen printing machine, a stationary squeegee, a screen mounted on a frame of circular cross section for movement beneath and in contact with said squeegee, an endless belt, means for supporting the belt in contact with said screen upon the inwardly facing surface of said screen, and means for deflecting said belt from the screen in the vicinity of said squeegee.

2. In a screen printing machine, a stationary squeegee, a screen mounted on a frame of circular cross section for movement beneath and in contact with said squeegee, an endless belt, means for supporting the belt in contact with said screen upon the inwardly facing surface of said screen, means for deflecting said belt from the screen in the vicinity of said squeegee, and means for driving said belt at substantially the same peripheral speed as said screen.

3. In a screen printing machine, a stationary squeegee, a screen mounted for movement in a closed path beneath and in contact with said squeegee, an endless belt supported in contact with the inwardly facing surface of said screen, and means for separating the belt from the screen at one zone to by-pass said squeegee.

4. In a screen printing machine, a screen, a frame for mounting said screen in the form of a cylinder and arranged for rotation, a non-r0- tatable frame within the first frame, an endless belt, and means carried by the second frame for supporting said belt in contact with the greater portion of the inwardly facing surface of said screen.

5. In a screen printing machine, a screen, a frame for mounting said screen and arranged for rotation, a non-rotatable frame within the first frame, a stationary squeegee, an endless belt, and means carried by the second frame for supporting said belt in contact with the greater portion of the inwardly facing surface of said screen.

6. In a screen printing machine, a screen, a frame for mounting said screen, means for rotating said screen frame, a non-rotatable second frame within the first frame, a plurality of rollers mounted in said secondary frame so spaced to support an endless belt in contact with the inwardly facing surface of said screen and separate said belt and screen in the printing area, an endless belt passing over said rollers in contact with the greater portion of the inwardly facing surface of said screen, means to drive one of said rollers moving the belt at substantially the same speed as the screen, a stationary squeegee positioned between said belt and screen at line of contact with the work piece and a doctor blade positioned to remove any excess printing material from the driven roller.

'7. In a screen printing machine, a general frame for supporting work pieces to be printed, a rotatable frame and a screen arranged thereon in cylindrical form, means for simultaneously rotating said second frame and rolling said screen across the face of a work piece supported on the first frame, a squeegee and means for supporting the squeegee to carry it across the face of the work piece with the creen interposed therebetween, and means bodily movable with said second frame as the screen rolls over the work piece for contacting and supporting the screen across its Width parallel to its axis of rotation immediately before and after its passage beneath said squeegee.

8. In a screen printing machine, a squeegee, a screen mounted for movement in contact with said squeegee, a movable belt supported incontact with the inwardly facing surface of said screen, and devices separating the belt from the screen at one zone to by-pass said squeegee.

9. In a screen printing machine, a squeegee, a screen mounted for movement in contact with said squeegee, a movable belt, devices supporting said belt in contact with said screen upon its inwardly facing surface, devices separating the belt from the screen at one zone permitting said belt to by-pass the squeegee and-devices driving said belt and screen at substantially the same peripheral speed at their points of contact.

10. In a screen printing machine, a squeegee, a screen mounted for movement beneath and in contact with said squeegee, a movable belt supported in contact with the inwardly facing surface of said screen, devices separating the belt from the screen at one zone to by-pass said squeegee and devices supporting said screen throughout its width shortly before and after its passage under said squeegee.

11. In a screen printing machine, a squeegee, a screen mounted for movement beneath and in contact with said squeegee, a movable belt supported in contact with the inwardly facing surface of said screen, devices separating the belt from the screen at one zone to by-pass said squeegee and devices supporting said screen throughout its width shortly after its passage unating with said rack and clutch, a non-rotatable second frame within the first frame comprising two circular end plates, a sleeve designed to be superimposed on the sleeve attached to the first frame fastened to said two end plates, means for preventing rotation of said second frame upon the axle of a supporting carriage, a plurality of rollers mounted between and supported by said end plates and positioned to support an endless belt in contact with the inwardly facing surface of said screen and separate said belt and screen in the printing area, an endless belt passing over said rollers in contact with the greater portion of the inwardly facing surface of said screen, means to drive one of said rollers comprising two gears, one thereof being a ring gear centrally attached to the inward face of the end plate of the first frame era-operating with the other gear attached co-axially to one end of a roller and of such pitch ratio that the belt i driven at substantially the same speed as the screen, "means for adjusting one of said rollers relative to the tension of the belt, an idle roller positioned to press against and prevent the slipping of the belt in its passage over the driven roller, a stationary squeegee supported by and between said end plates in the second frame, positioned between said belt and screen at the line of contact with the work piece, means for access to the interior of said second frame comprising several openings in the end plates, a doctor blade positioned to remove any excess printing material from the driven roller, a carriage mounted upon a frame, means for moving said carriage forward and backward upon said frame, a fixed axle supported insaid carriage upon which saidfirst and second 

